Whats it take to convert this gun to 45 super and is it worth doing, can I still shoot acp's? how does the super compare to the acp in size?

I converted a Series 80 Colt 1991-A1 to .45 Super (suprisingly still can shoot standard .45 ACP with Wilson mags.) I installed:
32# Wolff recoil spring (necessary)
EGW enhanced slide stop (probably necessary)
Wilson 1-piece SS guide rod (not necessary)
Wilson SS barrel bushing (not necessary)
Wilson 7- and 8-round mags (necessary).
I don't know what would be different for a Series 70, probably not much.

That, and a heavier set of weights to build up your forearms to be able to retract the slide.

Norm